Differentiated Expression Of Pathogenesis-related Enzymatic Activity In Two Apple Cultivars In Response To The Pathogen Marssonina Coronaria

China is the largest apple producer and marketing in the world and contributes todevelopment of the apple industry in the world. The Chinese apple industry plays animportant role in increasing income for Chinese farmers and improvement of ecologicalenvironment. Marssonina coronaria can lead to severe defoliation and causes a heavy loss inthe apple industry in China.Differential induction of the enzyme activity of seven pathogenesis-related proteins:chitinase (CHT), phenylalamine ammonia lyase (PAL), superoxide dismutase (SOD),polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT) and malondialdehyde (MDA)from leaf extracts was characterized in both resistant ‘Qinguan’ and susceptible ‘Fuji’ applecultivars at0,4,8,16,24,48,72and96h post-inoculation (hpi) with the pathogenMarssonina coronaria. These are major results from this study:1.Activity of all seven enzymes significantly increased in both the resistant and thesusceptible cultivar after inoculation with the pathogen (P <0.05). However, activityincrement after inoculation (AIAI) was very different among the seven proteins, ranging from52to173%in ‘Qinguan’ and34to137%in ‘Fuji’.2.AIAI of the seven enzymes in both cultivars had either one or two peaks at16hpi (CHTand PPO),24hpi (CAT, SOD, POD, PAL-‘Fuji’ and MDA),48hpi (PAL-‘Qinguan’ andCHT-‘Fuji’) or72hpi (CHT-‘Qinguan’). Correlation analysis showed that expression ofspecific enzymes was significantly correlated (P <0.05) with the other enzymes studiedwithin each apple cultivar.3.The correlation analysis for comparisons of pairs of AIAI of the seven enzymesthroughout the eight sampling times in each cultivar showed that eleven (48%) of twenty onecorrelation coefficients were significant in both ‘Qinguan’ and ‘Fuji’，only nine of elevenpairs of comparisons with significant correlation coefficients were the same between the twocultivars 4.Results from a principal coordinate analysis showed that CHT, SOD, PAL and MDAwere associated with one another in ‘Qinguan’, whereas PPO, POD, SOD and CAT wereassociated in ‘Fuji’. The associatoion patterns between seven enzymes were clearly discernedusing PCoA, which facilitates our better understanding interactions between apple plants andthe pathogen M. Coronaria.5.A T-test showed that the AIAIs of all seven enzymes were significantly differentbetween the two cultivars (P <0.05). The Mantel test showed that co-correlation coefficientsof AIAI of the seven enzymes on the whole was non-significant between ‘Qinguan’ and ‘Fuji’(Rxy=-0.318, P=0.060).6.Both AIAI and the association pattern among pathogenesis-related proteins on thewhole may be two important indicators that are contributing to resistance in apples inresponse to inoculation of M. Coronaria.This study adds to our knowledge of apple responses to M. coronaria and providesinformation to potentially control this disease in the future.